Circuit interrupter



Nov, 1?, i959 B. IMMEL ETAL K9115 5517 CIRCUIT INTERRUPTER Filed Oct.22, 1956 5 $heets-Sheet w. G 3 9 B 0 4 N I 2, Ma 2 2 3 3 w b u w m m Hall M5 3 w l 3 Z a ijjjj P.W a

INVENTORS Ralph B. Imm Marshal ATTORNEY wn'uesssk Dav WM Ea EMM EZL ETAL Nov. 17, 1959 v CIRCUIT INTERRUPTER 5 Sheets-Sheet 2 Filed Oct, 22,1956 NW. 17, i59

R. B. IMMEL ETAL CIRCUIT INTERRUPTER Filed 00%. 1956 I Sec.

m Arcing Time (60 Cycles Fig. 5.

3 Sheets-$heet 3 United States Patent CIRCUIT INTERRUPTER Ralph B.Immel, Williamsville, and Marshall P. White,

Cheektowaga, N.Y., assig'nors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application October 22',1956, Serial No. 611,448 Claims. or. 200-147 Our invention relates,generally, to electric circuit interrupters and, more particularly, tointerrupters of the type commonly known as contactors.

Practically all commercially available D.C. contactors utilize wire orstrap wound blowout coil assemblies for providing a magnetic field forlengthening the are drawn when a circuit is interrupted. A blowoutstructure of the prior type usually requires a large number of auxiliaryparts such as iron cores, insulating tubes and washers, iron plates,etc. These parts require considerable space and increase the cost of thedevice. Blowout coils are often the source of the greatest amount ofheat in a contactor and they may cause overheating. They also requireinsulation and clearance to parts of different polarity.

Prior contactors have usually been of the single-break type and requireda flexible connection between the moving contact member and the fixedcontact member. Woven shunts have been generally utilized for theflexible connections. These shunts have often become a major source oftrouble. The shunts have also been difficult to insulate from thecontactor frame.

An object of our invention, generally stated, is to provide an improvedinterrupting device which is small in size, efiicient in operation, andwhich may be economically manufactured and installed.

A more specific object of our invention is to provide an interruptingdevice which may be utilized in either A.C. or D.C. circuits.

Another object of our invention is to provide a contactor of thedouble-break type which is not aifected by the polarity or direction ofcurrent flow through the contact members.

A further object of our invention is to provide an interrupting devicehaving a single-piece insulating member for enclosing the circuitinterrupting members of the device.

Still another object of our invention is to provide a contactor havingimproved interrupting characteristics, particularly for low currentsassociated with highly inductive loads.

A still further object of our invention is to provide a contactor whichdoes not require the utilization of blowout coils and their associatedparts.

Other objects of our invention will be explained fully hereinafter orwill be apparent to those skilled in the art.

In accordance with one embodiment of our invention, a vertically movabledouble-break contact assembly is disposed in a single-piece insulatingbase having arc chambers therein which are identical in shape anddimensions. A permanent magnet, preferably of a ceramic type, isdisposed in a pocket in the base between the stationary contact members.The magnet creates a constant magnetic field which causes the arcs drawnbetween the two sets of contact members to move in opposite directions.When the polarity of the current or the magnet is reversed, thedirections of the arcs are reversed.

Patented Nov. 17, 1959 Since the arc chambers are identical, theinterruption is the same for either polarity. Therefore, the contactorcan be utilized in either A.C. or DC. circuits.

For a better understanding of the nature and objects of the invention,reference may be had to the following detailed description, taken inconjunction with the accompanying drawings, in which:

Figure 1 is a view, partly in front elevation and partly in section, ofa contactor embodying the principal features of the invention;

Fig. 2 is a view, in section, of the contactor shown in Fig. 1;

Fig. 3 is a view, in perspective, of the interrupting device for thecontactor, portions being broken away for clearness;

Fig. 4 is a diagrammatic view illustrating the principles of operationof the interrupting device, and

Fig. 5 is a set of curves illustrating the interrupting characteristicsof the present device as compared with prior devices.

The structure shown in the present drawings is an improvement over theinterrupting device described in a copending application of R. B. Immelet al., Serial No. 463,912, filed October 22, 1954, now Patent No.2,875,303, issued February 24, 1959. The interrupting device disclosedin the aforesaid application had horizontally mounted arc horns andrequired both an arc box and a base to enclose the interrupting members.The present structure requires only one ceramic or cold moldedinsulating member for supporting and enclosing the stationary contactmembers and are horns. Furthermore, the circuit interruptingcharacteristics are considerably improved by mounting the arc hornsvertically and providing identical arcing chambers as will be describedmore fully hereinafter.

As shown in Fig. 3, a one-piece base or are box 10 is provided with twoidentical arc chambers 11 and 12 each of which contains a verticallydisposed conductor or are horn therein. A conductor or arc horn 13 ismounted in the arc chamber 11 and an identical conductor or are horn 14is mounted in the arc chamber 12. As previously stated, the arc box 11may be molded from a ceramic or other suitable insulating material.

As shown in Figs. 1 and 2, the arc box may be mounted on a supportingpanel 15 by means of two bolts 16 which extend from the front of the arcbox through the box into the panel 15. The conductors 13 and 14 may beretained in the arc box by means of bolts 17.

As shown in Fig. 4, each conductor 13 and 14 has a stationary contactmember or portion 18 secured to the lower end of the conductor. Theconductor 13 has an integrally formed terminal portion 21 which isoffset from the vertical portion of the conductor and extends above thetop of the base 10 for making an electrical connection thereto.Likewise, the identical conductor 14 has a similar terminal portion 22for making an electrical connection. As shown, the arc chambers 11 and12 are opened at the top, thereby permitting gases to escape from thetop of the chambers.

As shown most clearly in Figs. 2 and 4, a generally U-shaped bridgingmember 23 has two contact members or portions 19 secured thereto forengaging the spaced stationary contact members 1 8. The bridging member23 is slidably disposed in a generally U-shaped yoke 24. As shown, thesides of the bridging member 23 are notched at 25 for receiving the legsof the yoke 24. The upper ends of the legs of the yoke 24 have inwardlyextending portions 26 for retaining the bridging member 23 in the yoke.A spring 27 is disposed between the base of the bridging member 23 andthe base of the yoke 24 to maintain a predetermined contact pressurebetween the contact members 18 and 19 when they are closed.

As shown in Figs. 1 and2, the yoke 24 is attached to an insulatingcarrier or cross bar 23 by means of a screw 29. The carrier 28 is movedvertically to engage the contact members 19 with the stationary contactmembers 18 by means of an electromagnetic device 31.

As shown in Fig. 2, the insulating carrier 28 is attached to a bolt 32by means of a bracket 33. The bolt 32 extends through a fixed portion 34of a solenoid core and is attached to a movable portion 35 of thesolenoid core. A cup-shaped insulating member 30 is disposed between thescrew 29 and the head of the bolt 32.

A coil 36, which surrounds the core of the solenoid, may be energized tocause the electromagnetic device to raise the carrier 28 and thebridging member 23. When the coil 36 is deenergized, a kickout spring 37assists gravity in lowering the cross bar 28 and separating the contactmembers 18 and 19. As shown, the spring 37 is disposed between a guidewasher 38 for the core 35 in the base of the electromagnetic device 31and a washer 39 attached to the core 35 by the bolt 32. Thus, the spring37 is compressed when the coil 36 is energized to move the core 35upwardly.

As shown more clearly in Figs. 2 and 3, a permanent magnet 41 isdisposed in a separate compartment 42 in the base or are box 10. Themagnet 41 is located between the conductors 13 and 14 and extends belowthe stationary contact members 18. Thus, the bridging member 23straddles the magnet 41 when the contact members are closed. The magnet41 is preferably of a ceramic type, for example one composed of amagnetic mixed oxide compound having the formula BaO.6Fe O The magnet 41may be composed of any suitable magnetic material, but, the ceramicmaterial is preferable because of its lower cost, resistance todemagnetization and high electrical resistivity.

The basic principles of the arc interrupting device are illustrated inFig. 4. Assuming that the magnet 41 is disposed in the arc chamber withits polarity as indicated by the letter N, the magnetic field set up bythe magnet is illustrated by the broken lines and arrows. Also, assuming that the instantaneous alternating current or direct current flowthrough the conductors 21 and 22 and the bridging member 23 is as shownby the arrows, an are drawn between the front contact members 18 and 19is moved to the left and upwardly along the arc horn 13 because of themagnetic field and the thermal rise of the hot gases. An are drawnbetween the rear contact members 18 and 19 will move to the right andupwardly along the arc horn 14 because of the same forces.

The arcs move in arcing chambers which are identical in both size andshape. As shown in Fig. l, the conductor 13 is disposed midway betweenthe sidewalls of the arc chamber 11. Furthermore, the sides of the arcchamber are symmetrical in size and shape. Likewise, the conductor 14 isdisposed midway between sidewalls of the arc chamber 12. As previouslystated, the chambers 11 and 12 are identical in shape and dimensions.

When either the magnetic =field or the terminal polarity is reversed,the arc drawn between the front contact members 18 and 19 will move tothe right and the rear arc will move to the left. If both the magneticfield and the terminal polarity are reversed, there will be no change inthe arc movement. Therefore, the present device will operatesatisfactorily no matter how the magnet 41 is placed in the structurewith respect to its polarity or to which polarity the terminals 21 and22 are connected. Accordingly, the present device can be used on eitheralternating current or direct current circuits. Since identical arcingchambers are provided on both sides of the stationary conductors andcontact members, there are no differences in. he interruptingcharacteristies for either AC. or D.C.

4. Furthermore, the interrupting characteristics are greatly improvedover those of prior devices. The blowout field of prior contactorshaving series wire or strap wound blowout coils varies directly with thecurrent. With low currents and highly inductive loads, the currentinterruption is poor. With the constant magnetic blowout field providedby the permanent magnet in the present device low currents associatedwith highly inductive loads have been satisfactorily interrupted. Thepresent device does not require conducting plates or pole pieces inaddition to the magnet 41 as the leakage of the magnet is effective inextinguishing the arcs.

The difference between the operating characteristics of the old devicesand the present device is illustrated by the curves shown in Fig. 5 inwhich arcing time is plotted against current. Curve 1 illustrates thecharacteristics of the present device and curves 2 and 3 illustrate thecharacteristics of two prior devices having different current ratingsand a different number of turns in their blowout coils. From curve 1 itwill be seen that the interrupting time of the present device decreaseswith the current. From curves 2 and 3 it will be seen' that theinterrupting time of the prior devices increases as the currentdecreases so that the arc hangs on and is not extinguished at low valuesof current.

As shown in Fig. 1, auxiliary contact members 45 and 46 may be mountedon the cross bar 28 to engaged fixed contact members 47 and 49,respectively, when the cross bar is actuated to actuate the main contactmembers of the contactor. The auxiliary contact members 45 may be of thenormally open type and the contact members 46 may be of the normallyclosed type. Thus, the auxiliary contact members are operated inconjunction with the main contact members, and they may be utilized incontrol or indicating circuits in a manner well known in the art.

From the foregoing description, it is apparent that we have provided aninterrupting device which has excellent arc interruptingcharacteristics. The present device is relatively small in size and of asimple and rugged construction. Therefore, it is suitable forutilization in electromagnetic contactors which are requlred to functionunder severe operating conditions. Furthermore, the present device maybe manufactured at a relatively low cost.

Since numerous changes may described construction and differentembodiments of the invention may be made without departing from thespirit and scope thereof, it is intended that all matter contained inthe foregoing description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit interrupter comprising a single-piece insulating memberhaving two are chambers therein, each chamber being open at the top andhaving totally enclosing side walls, a single stationary contact memberin each arc chamber, a combined terminal and are horn for the contactmember in each arc chamber, a permanent magnet disposed between saidcontact members, a bridging conducting member having a contact memberthereon for engaging each stationary contact member, electromagneticmeans for raising said bridging member to engage the contact membersthereon with said stationary contact members, and spring means forlowering the bridging member to disengage said contact members and drawarcs between the contact members, said magnet causing an arc to travelup one side of each arc horn during one polarity of the arc current andup the opposite side of the arc horn during another polarity of the arccurrent.

2. In an interrupting device, in combination, an insulating arc boXhaving two are chambers therein, said arc chambers being open at the topand identical in shape and dimensions, only one elongated vertically disbe made in the above posed conductor in each arc chamber and extendingthrough the open top of the chamber, said conductors being identical inshape and dimensions, each conductor being equidistant from oppositesides of its chamber, a stationary contact member on the lower end ofeach conductor, a pennament magnet disposed in a separate compartment insaid insulating member between said conductors, and a vertically movablebridging conducting member having a contact member thereon for engagingeach stationary contact member.

3. In an interrupting device, in combination, an insulating arc boxhaving two are chambers therein, said arc chambers being substantiallyidentical in shape and dimensions and open at the top, only oneelongated conductor vertically disposed in each chamber equidistant fromopposite sides of the chamber, each conductor having an integrallyformed terminal portion offset laterally from the upper end of theconductor and extending above the top of the insulating member, astationary contact member secured on the lower end of each conductor, apermanent magnet disposed in a separate compartment in said insulatingmember between said conductors, and a vertically movable conductingmember having spaced contact members thereon for engaging saidstationary contact members.

4. In an arc interrupting device, in combination, an arc box having atleast two are chambers therein, said are chambers being substantiallyidentical in shape and dimensions, only one elongated generally flatconductor vertically disposed in each chamber equidistant from oppositesides of the chamber, a stationary contact portion at the lower end ofeach conductor, a movable contact member separable from each stationarycontact portion to draw an arc therebetween, and permanent magnet meansfor producing a magnetic field which moves the arc to a position whereone end of the arc travels upwardly along one side of said conductorduring one polarity of the arc current and along the opposite side ofthe conductor during another polarity of the are current.

5. In an interrupting device, in combination, a singlepiece moldedinsulating member having two are chambers therein, said are chambersbeing substantially identical in shape and dimensions, each chamberbeing open at the top and having totally enclosing side walls, only oneelongated conductor having opposite sides vertically disposed in eachchamber equidistant from opposite sides of the chamber, a stationarycontact member secured on the lower end of each conductor, a permanentmagnet disposed in a separate compartment in said insulating memberbetween said conductors, and a vertically reciprocable conducting memberhaving spaced contact members thereon for engaging and disengaging saidstationary contact members, said magnet causing arcs drawn in said arechambers to change sides on said conductors with a reversal of thepolarity of the arc current.

References Cited in the file of this patent UNITED STATES PATENTS (2ndaddition to 981,687)

